问题
What is this icon?
Some codes are "hidden" because of this icon, when I click it, the IDE pops up the code snippet that's supposed to be there before, since codes disappeared, I can't reference it from other files either.
回答1:
If you are using a version control system (such as Git) in the project you are working on with the IDE, you will see these marks on the files (See sample images below).
File content
- Grey triangles: deleted content
- Blue rectangles: changed content
- Green rectangles: added new content
These are seen when the changes are not yet committed. Once all the changes are committed the marks are gone.
If you click on those marks you will see the content that was there before the change took place.
Files
The same principle is applied for files (see below images)
- Green: new file
- Blue: modified file
- Grey: deleted file
While working you see the files like this (deleted ones are omitted):
And, in the time of committing changes you will see them like this (you see all files changed):
See official doc for more info.
来源：https://stackoverflow.com/questions/45154073/whats-this-grey-triangle-arrow-means-in-intellij